It doesn't have to be attacking or anything, you can just invest some mana to kill off stuff
A lynchpin in White Weenie aggro decks of the time, Adanto Vanguard was played alongside another Vampire card (in the loosest sense), Legions Landing
I always liked how nobody wants to spend removal on it right away
If a player is instructed to put a card into their graveyard from their library without using the word "mill," (by the effect of Rowan's Grim Search from Wilds of Eldraine , for example), that card isn't a legal target for Tato Farmer's last ability
Atlas ability to turn mana investments into huge threats lets you cheat out your biggest dinosaurs for a fraction of the cost
Such swift ramp is invaluable, especially in mono-white, where efficient mana utilization can dictate the pace of the game, and ramp is much harder to come by than say, green or black